Although a considerable amount of effort has been given to the production of corrugated thin metal foil converters in which the successive layers of foil are nonnesting as, for example, in U.S. Pat. No. 4,725,411 dated February 16, 1988, little attention has been paid to the use of corrugated thin metal foil layers which are normally nesting. Our-pending application Ser. No. 089,578 filed August 26, 1987, now issued as U.S. Pat. No. 4,869,738, provides one method of keeping normally nesting layers in spaced relation utilizing sized spherical bodies, e.g., small stainless steel spheres, dispersed in the washcoat of refractory metal oxide, e.g., alumina. However, some difficulty in maintaining a single thickness of the small spheres has been experienced, and an improved means for maintaining normally nestable corrugated layers in spaced relation other than a flat layer of foil (which is common in such cases) has now been found.
It has been found that an improved converter having layers of normally nesting corrugated thin metal may be fabricated and inexpensively made by corrugating a thin metal strip with regular straight or patterned corrugations and which will nest together if layered, cutting the strip into segments of desired length, and superimposing on the segments two or more fibers or bundles of fibers to prevent nesting. The fiber or fibers may be metal or ceramic or ceramic/cermet. They can be formed to conform to or mesh with the corrugations, i.e. have the same profile. The preferred metal is ferritic stainless steel or aluminized stainless steel wire having a diameter equal to from 0.25 times the amplitude of the corrugations up to 3.0 times such amplitude. The ceramic or cermet fibers are generally in the form of threads formed of many fibers which fibers are from 0.5 to 3 microns in diameter.
Reference may be had to U.S. Pat. No. 4,707,399 dated November 17, 1987 to Rambosek; to U.S. Pat. No. 4,652,286 dated March 24, 1987 to Masaaki; to U.S. Pat. No. 4,585,500 dated April 29, 1986; to U.S. Pat. No. 4,511,664 dated April 16, 1985; to U.S. Pat. No. 4,166,147 dated August 28, 1979; to U.S. Pat. No. 4,047,965 dated September 13, 1977; U.S. Pat. No. 3,795,524 dated March 5, 1974 and to U.S. Pat. No. 3,709,706 dated January 9, 1973 for disclosures of nonvitreous inorganic or metal oxide ceramic fibers which may be formed into multistrand threads of the desired thickness (0.5 to 2.5 times the amplitude of the corrugations) and used as the spacing elements in the converters of the present invention. These U.S. Patents are incorporated herein by reference thereto.